1. Technical Field
This disclosure relates to echo reduction. In particular, this disclosure relates to echo reduction and suppression of residual echo signals in communication systems.
2. Related Art
Echo reduction or suppression may be needed in communication systems, such as hands-free sets and speech recognition systems. Communication systems may include a microphone that detects a desired signal, such as a speech signal from a user. The microphone may also detect undesirable signals, such as echoes produced by a loudspeaker.
Echoes may occur through the repetition of sound carried by the reflection of sound. Such signals may be detected by the near-end microphone and re-transmitted back to the remote party.
Multi-channel systems may have performance problems when individual channels have a correlation, which may occur when multiple microphones detect the speech from a speaker. When the individual channels are correlated, the adaptive filters may not converge to the desired impulse response. This may occur because portions of signals output by one loudspeaker may be compensated by a filter that processes the output of a different loudspeaker.
Optimization of echo compensation filters may depend upon the position of a speaker. Movement of the speaker may require recalculation of the filter coefficients. Filter convergence problems may result from the non-uniqueness of the adaptation calculations. Some approaches may delay the signals in individual channels and may introduce a non-linearity in the channel paths. These methods may introduce audible artifacts that reduce the quality of the speech signal. A need exists for an echo reduction system to reduce echoes in a multi-channel environment.